Efficacy and safety of leuprorelin acetate 6-month depot, TAP-144-SR (6M), in combination with tamoxifen in postoperative, premenopausal patients with hormone receptor-positive breast cancer: a phase III, randomized, open-label, parallel-group comparative study

Background Leuprorelin acetate, a luteinizing hormone-releasing hormone agonist, is used worldwide in premenopausal women with hormone receptor-positive breast cancer. This study was conducted to assess the non-inferiority of the 6-month depot formulation, TAP-144-SR (6M) 22.5 mg to the 3-month depot formulation, TAP-144-SR (3M) 11.25 mg in postoperative, premenopausal patients with hormone receptor-positive breast cancer. Methods This was a 96-week phase III, randomized, open-label, parallel-group comparative study. All patients concomitantly received oral tamoxifen (20 mg daily). The primary endpoint was the suppression rate of serum estradiol (E 2 ) to the menopausal level (≤30 pg/mL) from Week 4 through Week 48. Results In total, 167 patients were randomized to receive TAP-144-SR (6M) ( n = 83) or TAP-144-SR (3M) ( n = 84) and the E 2 suppression rate was 97.6 and 96.4 %, respectively. The estimated between-group difference was 1.2 % (95 % confidence interval −5.2 to 7.8). The non-inferiority of TAP-144-SR (6M) to TAP-144-SR (3M) for E 2 suppression was confirmed. As for safety, common adverse events were hot flush and injection site reactions including induration, pain, and erythema in both treatment groups, which were of ≤Grade 2 in severity and not serious. No significant between-group differences in safety profiles and tolerability were observed. Conclusions TAP-144-SR (6M) was not inferior to TAP-144-SR (3M) for its suppressive effect on serum E 2 . TAP-144-SR (6M) was also as well tolerated as TAP-144-SR (3M).